dm: dec_pending needs locking to save error value (f88fb981) · Commits · 戴 / test

Multiple instances of dec_pending() can run concurrently so a lock is needed when it saves the first error code. I have never experienced actual problem without locking and just found this during code inspection while implementing the barrier support patch for request-based dm. This patch adds the locking. I've done compile, boot and basic I/O testings. Cc: stable@kernel.org Signed-off-by:

Kiyoshi Ueda <k-ueda@ct.jp.nec.com> Signed-off-by:

Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Signed-off-by:

Alasdair G Kergon <agk@redhat.com>

drivers/md/dm.c

+8 −2

Original line number	Diff line number	Diff line
		@@ -47,6 +47,7 @@ struct dm_io {
		atomic_t io_count;
		struct bio *bio;
		unsigned long start_time;
		spinlock_t endio_lock;
		};

		/*
		@@ -578,8 +579,12 @@ static void dec_pending(struct dm_io *io, int error)
		struct mapped_device *md = io->md;

		/* Push-back supersedes any I/O errors */
		if (error && !(io->error > 0 && __noflush_suspending(md)))
		if (unlikely(error)) {
		spin_lock_irqsave(&io->endio_lock, flags);
		if (!(io->error > 0 && __noflush_suspending(md)))
		io->error = error;
		spin_unlock_irqrestore(&io->endio_lock, flags);
		}

		if (atomic_dec_and_test(&io->io_count)) {
		if (io->error == DM_ENDIO_REQUEUE) {
		@@ -1226,6 +1231,7 @@ static void __split_and_process_bio(struct mapped_device md, struct bio bio)
		atomic_set(&ci.io->io_count, 1);
		ci.io->bio = bio;
		ci.io->md = md;
		spin_lock_init(&ci.io->endio_lock);
		ci.sector = bio->bi_sector;
		ci.sector_count = bio_sectors(bio);
		if (unlikely(bio_empty_barrier(bio)))

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